Health Benefits of Antioxidants
Antioxidants are the body’s first line of defence against illness and disease. They are naturally produced by the body to defend against free radicals and are believed to prevent certain types of cell damage that lead to heart disease and cancer. The discovery of antioxidants is still relatively new in biochemistry terms. They were first identified in the 1990’s so much of the research is still ongoing or in its early stages. In order to fully understand the role of antioxidants, we first need to know a bit more about free radicals.
Atoms and Free Radicals
When reading about or shopping for antioxidant-rich foods you will often see references to free radicals. But what are they and why do they have such a bad reputation?
Stable atoms have eight electrons, which are carried in pairs. Unfortunately, atoms can be damaged by the oxidation process (exposure to oxygen) which causes them to lose electrons and become unstable free radical particles. When this occurs, unstable atoms steal electrons from neighbouring cells, which radically alters their structure and function. As this process continues, it creates a chain reaction as cell after cell becomes affected and damaged. Occasionally cells are permanently damaged which accelerates the ageing process and increases the risk of certain diseases.
Unfortunately, we can’t avoid free radicals completely; they are naturally produced by the body’s oxidation process and conversion of food into energy. Environmental factors can also play a part, such as cigarette smoke, exercise. pollution, cosmetics, and sunlight.
The oxidation process
In simple terms, oxidation is the process of things breaking down, for example, oxidation occurs when iron rusts or an apple goes brown. Oxidation is an essential part of many bodily functions, such as burning energy and making new cells, all of which produce free radicals. Oxidative stress occurs when free radicals run rampant with insufficient antioxidants to halt the chain reactions. Essentially, if the body fails to produce sufficient antioxidants, the damage continues to spread.
What are Antioxidants?
We aren’t defenceless against free radicals - the body naturally produces antioxidants to counteract them and keep their numbers in check. The term antioxidant refers to the way in which certain compounds work. Antioxidant compounds have the ability to donate spare electrons to free radicals to stabilise them and prevent them from causing further damage to neighbouring cells. Because antioxidants remain stable even when they are missing electrons, they don’t become free radicals themselves when giving electrons away.
There are hundreds of different types of substances that act as antioxidants, such as vitamins C and E, beta-carotene, selenium, Coenzyme Q10, lipoic acid, and polyphenols. Each one is different and so supports the body in its own way. This is why many different types of antioxidants are needed from the diet because one type simply won’t be that effective on its own.
Benefits of Antioxidants
Over the past few years, there has been plenty of hype surrounding the potential health benefits of antioxidants. While some of the claims are completely unfounded, it does appear that adding more antioxidants to the diet offers some health benefits, particularly in relation to age-related conditions. Here are a few of the ways that antioxidants are thought to support health:
- Heart problems: Antioxidants may help to prevent cholesterol in the blood stream from becoming oxidised by free radical particles. When LDL (bad) cholesterol is oxidised it becomes ‘sticky’ and starts to build up along artery walls, which increases the risk of atherosclerosis, heart disease and stroke. Eating certain types of antioxidant-rich fruits and vegetables has been shown to reduce the effects of this process and maintain flexible artery walls.
- A Swedish observational study of 32,000 women found that those who ate an average of 7 daily servings of antioxidant-rich fruits and vegetables over a 10 year period had a 20% lower incidence of heart attacks compared to women who ate less than 2.4 servings. Grape seeds, in particular, are thought to support heart function. The seeds contain antioxidant proanthocyanidins, which are part of the flavonoid family and have been shown to reduce total cholesterol by an average of 10.7 mg/dL over an 8 week period. Other important antioxidant nutrients include resveratrol and EGCG.
- Vision: There are strong links between certain antioxidants and the prevention of age-related vision loss. The AREDS (Age-Related Eye Disease Study) led by the National Eye Institute in the US found conclusively that a combination of antioxidant vitamins C and E, zinc and beta-carotene reduced the risk of age-related macular degeneration (AMD) by 25%. A follow-up study including lutein and zeaxanthin found that these antioxidant carotenoids further improved the effectiveness.
- Skin health: Free radicals are a leading cause of premature ageing of the skin. Antioxidants help to prevent the oxidation of skin cells and so may help the skin to retain its elasticity and plumpness with age. Vitamins C and E support the production and maintenance of collagen in the skin while lycopene is a carotenoid found in red fruits and vegetables which also supports collagen production and helps to reduce damage to DNA. Antioxidants can be taken in various forms, from oral supplements and tinctures to topical creams and oils.
- Immunity: Free radicals can damage the immune cells themselves or interrupt their ability to communicate with each other, which results in an impaired immune response and causes the body to feel run down and overworked. Much of the research to date has focused on vitamin C and zinc, which may help to boost the immune system ahead of time and reduce the frequency and severity of colds and flu.
- Brain function: There is some evidence that increasing intake of fruits and vegetables may offer benefits for long-term memory and mental clarity, and reduce the risk of common neurodegenerative conditions such as Alzheimer’s and Parkinson’s. Green tea contains L-Theanine which is thought to increase the activity of a neurotransmitter called GABA and works to improve brain function, while the antioxidant quercetin, found in apple and blueberries, shows some promise at protecting against Alzheimer’s. However, the research is ongoing.
- Cancer: Antioxidants are widely touted as cancer-busters but to date, there is insufficient evidence to support their use, with several short-term trials that have so far shown largely no effect on cancer rates.
Types of Antioxidants
The antioxidants that the body produces naturally aren’t enough, and so the body needs a constant supply of antioxidants from the diet. Different types of antioxidants can be broken down into five categories; enzymes, vitamins, minerals, proteins and phytochemicals.
- Enzymes: Sourced from proteins and minerals. Some of the most effective antioxidant enzymes include Coenzyme Q10 and DHEA.
- Vitamins: Not all vitamins act as antioxidants, but those that do include vitamins A, C and E, and beta-carotene.
- Minerals: Again, not all minerals act as antioxidants. Those that do include copper, manganese, iodine, zinc and selenium. Antioxidant minerals often act as co-factors for the synthesis of enzymes.
- Proteins and amino acids: Important proteins and amino acids include alpha lipoic acid and glutathione.
- Phytochemicals: Many plants naturally produce antioxidants to protect themselves against free radicals. Unlike the others types of antioxidants above, phytochemicals are not considered to be an essential part of the diet, however, many studies show benefits from adding them to the diet. Important phytochemical families include carotenoids, flavonoids and polyphenols.
Food Sources of Antioxidants
There is strong evidence to show that diets rich in antioxidants can lower the risk of heart disease, stroke, cancer, and age-related eye disease. While fruits and vegetables contain a wide array of antioxidant compounds, their colour often indicates their main antioxidant content. The different colours provide different types of antioxidants, which is why it’s important to ‘eat the rainbow’ instead of limiting yourself to one or two types of fruit and veg.
- Greens - spinach and broccoli - while these are packed with a wide array of vitamins and minerals, they are also particularly useful sources of lutein and zeaxanthin, which are essential for eye health. Leafy greens are great for all round health and the immune system.
- Red - tomatoes – many red fruits and vegetables are loaded with lycopene, which gives them their rich colouring. Lycopene has been shown to reduce the risk of heart disease and stroke and may help to protect DNA from damage.
- Orange and yellow – carrots and sweet potatoes – these foods are good sources of beta-carotene and vitamin C, and so offer many benefits for the maintenance of the skin, immune system and digestive system.
- Purple and blue – prunes, aubergine, berries – their anthocyanin content gives these fruits and vegetables their deep colouring. Anthocyanins have been closely linked with reduced risk of certain types of cancers, heart disease and cognitive decline. Cranberries are rich in a certain type called pro-anthocyanidins, which are known to support urinary tract health.
Fruits and vegetables with high levels of antioxidants are often referred to as ‘superfoods’. Currently, there are no set criteria for what is deemed a superfood and so the term has been criticised for being more of a marketing tool. But there are foods that are known to provide a high concentration of antioxidants and are beneficial for health.
The antioxidants in fruits and vegetables can be damaged by cooking or processing, so they are best eaten raw. If cooking, opt for steaming to preserve the delicate antioxidant content as much as possible. Antioxidant supplements may offer added protection, however, they should never be taken as an alternative to a healthy diet or medication.
What Is an ORAC Value?
ORAC units were introduced to measure the antioxidant capacity of foods, so you may have come across them when reading about the nutritional benefits of superfoods. However, there has been controversy concerning their use. The units can vary depending on the amount of food which is measured; a flaw that was abused by a number of food marketers. So we prefer not to reference ORAC values when writing about antioxidant rich foods.
How Many Antioxidants do I Need?
This is where the evidence becomes problematic. We know that antioxidants are beneficial, but we don’t know how many antioxidants are needed for certain health benefits. It is clear that eating a diet rich in different fruits and vegetables can help and many of us are familiar with the ‘5 a day’ mantra, which most experts believe is sufficient to get all the antioxidants you need.
The UK government’s recommendations for a healthy balanced diet are highlighted in the Eatwell Plate below, which suggests that fruits and vegetables should make up one-third of your meal. While this doesn’t need to be every meal, it should balance out over the day or week.
However, there are differing opinions regarding how many portions of fruits and vegetables we should all eat on a daily basis. Some suggest '5 a day', while others suggest '7 a day' (5 veg and 2 fruit). While the jury is still out, simply try to incorporate as many different types and colours as you can. Antioxidants don’t survive in the body for long, so a regular daily supply is required.
Side Effects and Interactions
Antioxidant-rich fruits and vegetables pose few, if any, safety risks. However, questions have been raised over the safety of super strength doses of certain antioxidant supplements. There is some evidence to suggest that high doses of beta-carotene in supplement form may increase the risk of lung cancer in smokers so high-strength supplements are not recommended. It has also been suggested that super high doses of vitamin E may increase the risk of prostate cancer in men. Research is ongoing.
Antioxidant supplements may also interact with certain prescription medications, for example, high dose vitamin E supplements may increase the risk of bleeding, so should not be taken in combination with anti-coagulant medication. If you are concerned about a specific supplement, speak to your GP or pharmacist who will be able to provide medical advice to suit your individual needs.